e36 ignition coil on cylinder 4 melting / burning

**Denjeesi** · 08-13-2018, 10:52 AM

Hello,

I have a problem with my 1994 e36 320i (M52 engine).

First of, my English is not the best sorry about that.

So I took my car for a drive 2 days ago, nothing wrong, and parked it in the garage.
The following day, I started it and drove it a couple of minutes. Soon I noticed that it sounded like a subaru rather than a e36 so I knew it was misfiring. On my way back home I smelled burnt rubber and the engine was smoking. As I opened the hood I saw that the Ignition coil on cylinder 4 was completely melted, the whole top part. I let it sit over night, the following day I removed the coil and replaced it with a new one. As I started the engine it was idling super rough, more then before with just 5 cylinders working. When I hit the gas and went up in rpm, it drop down very slowly. Also I noticed that the coil was getting very hot. I tried this with 3 other ignition coils, and even replaced the spark plugs, didn't change anything, the problem occurs only on cylinder 4.

really don't know what to do next. Does somebody know where this problem is coming from?

Thanks

**ed323i** · 08-13-2018, 02:03 PM

If you've changed both the spark plug and the coil, then I'd guess perhaps some electronics in the DME have gone bad and the DME is now ordering the coil to fire constantly, overheating it?
Or something in the wiring, a short?

I can't really imagine what would cause this to happen in a mechanical sense, i.e. something going wrong inside the cylinder w.r.t. piston, valves, etc.. So, my bet is that something is going wrong electronically.

**E36328Coupe** · 08-13-2018, 03:06 PM

Loose plug? Exhaust gas cooking coil?

**Eric93se** · 08-13-2018, 03:53 PM

Probably a short in the DME. Did the car get hit with super heavy rain storms?

**Denjeesi** · 08-15-2018, 05:14 PM

That was what I was thinking, must be electrical hmm.. Is it possible that a bad ground connection could cause this?

How do I install a new dme? Can I just order one or does it have to be "adapted" to the car?

The only thing i can think of are the snowstorms in January, it sat outside for a 2 days, since I haven't been driving a lot.

**ed323i** · 08-15-2018, 06:00 PM

Depends.. If it's an early M50 320i, and your car has no EWS, then it's real easy. Just go to the local junkyard and get a DME with the same p/n and install it. And off you go. Can be from an E34 520i (1990 onwards) or E36 320i.
If your car has EWS and your engine is M52, then look up the link in my signature and get a pre-chipped DME with EWS-delete (select the M52B20 one). Then it's also plug&play (well, you need to cut one wire and the drive-away protection won't work anymore), and you'll gain some 10 HP and an improved torque curve at all rpm's. Or, you can just get one from the junk yard (E36 320i and early E39 320i) and then buy an OBD2-USB adapter and the 20-pin-to-ODB adapter and then using your Windows laptop resync the EWS to your new DME with a very simple tiny program (no need to install full INPA/EDIBAS and whatever). A DME, especially a 320i one, should be available for like 50-100 euro I'd say.

P.S. Before you go and buy another DME, do some simple checks on the wiring with a multimeter. Check the coil connector (wiring) and see if you find different ohms/volts compared to the coil connectors of the other cylinders. Then also, disconnect the DME and check again. To make sure there are no strange shorts or wires intertwined with the copper open.

**Denjeesi** · 08-15-2018, 06:39 PM

I have an 320i from November 1994. I don't think it has EWS. I also don't have an electronic key. So its basically plug n play then, great

Alright, I will take a closer look tomorrow morning.

When I disconnect the DME and open it, is there anything I should look out for that could indicate that its bad?

**Eric93se** · 08-15-2018, 07:20 PM

You should disconnect the negative on the batt before taking it out.

If you have oxide tracks (white residue) you can clean them off with denatured alcohol (use a clean paint brush and clean the whole thing) you have to make sure it's 1000% dry before putting it back in the car to test it. Give it a full 24hrs in a warm dry place.

**ed323i** · 08-15-2018, 07:41 PM

If you see the DME has been wet, then you know the cause.. Make sure you clean all leaves and debris in the channels near the firewall, passenger side.
If you look at the DME print and you see black/burned stuff, then you know enough.. But it might also look pristine and only an electronics expert could figure it out where/what went wrong. You might want to look specifically at the coil circuit for cylinder 4. Perhaps you can trace it from the DME connector if you know which pin it is.

Once you know the DME number (and do a search on google) you are probably fairly sure to know if it's an EWS-protected DME (EWS sync or EWS delete needed) or if it's a DME without any protection (plug & play).

Good luck!

You can still think of upgrading the EPROM chip in the DME.. Then it's a really cheap upgrade (just open the DME, remove old chip, and install new chip which only costs 30-40 euro). Check all ads of the ebay-guy linked in my signature, once you know the DME number.. Those 10HP, and especially the improved torque curve help a lot with the 2 liter engine. It will turn your 320i into a virtual 322i.. You'll notice the difference.
P.S. You probably have the Siemens MS40 DME and M50TU Vanos engine. Then you'd need this one https://www.ebay.es/itm/BMW-Chip-Tun...gAAOSw1VJZxLls . But first go and check the DME number.

**Denjeesi** · 08-16-2018, 01:15 PM

Ok so I was further investigating the problem with a friend of mine, we have checked all the wires from the plug to ecu, everything alright. Then opened the cpu, no visible damage.

So I called a mechanic from my local bmw garage and he said that I might have compression on cylinder 4, that is why the fuel mixture is not always firing. The coil is overheating because it needs more power to ignite the mixture, that is how I understood it atleast.

What do you guys think about this theory?

**E36328Coupe** · 08-16-2018, 01:24 PM

Originally Posted by Denjeesi

I have an 320i from November 1994. I don't think it has EWS.

Your car has EWS, it's just EWS I not EWS II
EWS but no transponder in the key

**ed323i** · 08-16-2018, 05:54 PM

Originally Posted by Denjeesi

Ok so I was further investigating the problem with a friend of mine, we have checked all the wires from the plug to ecu, everything alright. Then opened the cpu, no visible damage.

So I called a mechanic from my local bmw garage and he said that I might have compression on cylinder 4, that is why the fuel mixture is not always firing. The coil is overheating because it needs more power to ignite the mixture, that is how I understood it atleast.

What do you guys think about this theory?

I don't think that's a very plausible explanation. Haven't ever heard anybody experience something like that.. I think you can test an ignition coil with a mounted spark in the open air (at zero compression) for a very long time before the coil would start to overheat. I think the only reasonable explanation would be that the ignition driver in the DME died/shorted, and/or a short in the wiring.

But hey, wouldn't harm to have him test the compression anyways. So you know how healthy the engine is.

Perhaps you can test with the engine running. Unplug one coil connector and measure voltage at the pins. See if you find a difference between cylinder 4 and other cylinders.
If you know someone who has and knows how to use an oscilloscope, then use that and see if a different pattern shows, comparing cylinder 4 to the other cylinders.
What you want to compare is the dwell time, i.e. how much time does the DME send a +12V signal to the coil, so the coil can later send the spark to the spark plug. You'll probably find the dwell time in cylinder 4 to be too long, or the voltage too high. Or perhaps that there is continuous +12V voltage instead of a voltage fluctuating between 0 and 12V.

**Eric93se** · 08-16-2018, 07:13 PM

Your BMW mechanic is an idiot.

If you're sure all the wiring is good then the problem is in the DME. If you can take some quality pics of the inside, we can take a look.

**E36328Coupe** · 08-17-2018, 03:00 PM

Originally Posted by Eric93se

Your BMW mechanic is an idiot.

If you're sure all the wiring is good then the problem is in the DME. If you can take some quality pics of the inside, we can take a look.

Or the OPS translation / understanding is wrong because what was written is not plausible, e.g. "might have compression on cylinder 4", the op better had have compression on cylinder 4.

**Denjeesi** · 08-18-2018, 12:22 AM

Good Idea, I will measure the voltage again while the engine is running.
I'm also going to check compression, just in case.

I will keep you updated!

**Denjeesi** · 08-18-2018, 04:45 AM

Originally Posted by E36328Coupe

Or the OPS translation / understanding is wrong because what was written is not plausible, e.g. "might have compression on cylinder 4", the op better had have compression on cylinder 4.

Sorry, in our language we say the engine has compression, but actually mean that it is loosing compression on one or more cylinders.

**E36328Coupe** · 08-18-2018, 07:36 AM

Originally Posted by ed323i

I don't think that's a very plausible explanation. Haven't ever heard anybody experience something like that.. I think you can test an ignition coil with a mounted spark in the open air (at zero compression) for a very long time before the coil would start to overheat. I think the only reasonable explanation would be that the ignition driver in the DME died/shorted, and/or a short in the wiring.

But hey, wouldn't harm to have him test the compression anyways. So you know how healthy the engine is.

Perhaps you can test with the engine running. Unplug one coil connector and measure voltage at the pins. See if you find a difference between cylinder 4 and other cylinders.
If you know someone who has and knows how to use an oscilloscope, then use that and see if a different pattern shows, comparing cylinder 4 to the other cylinders.
What you want to compare is the dwell time, i.e. how much time does the DME send a +12V signal to the coil, so the coil can later send the spark to the spark plug. You'll probably find the dwell time in cylinder 4 to be too long, or the voltage too high. Or perhaps that there is continuous +12V voltage instead of a voltage fluctuating between 0 and 12V.

All what he said above. A coil has to generate less voltage to jump a smaller gap or one in lower compression environment.

**Denjeesi** · 08-18-2018, 01:45 PM

Here are some pictures from the DME:
https://drive.google.com/folderview?...zKsAoUSR-SiJE7

so normally this one would fit my car? : https://rover.ebay.com/rover/0/0/0?m...2F173460871290

**Eric93se** · 08-18-2018, 02:14 PM

Nothing visually wrong with the DME, a transistor must have failed. That ebay dme looks like it's identical.

**ed323i** · 08-18-2018, 02:24 PM

Oh, wait, you have an M52 engine.. I think the manufacture date is incorrect then, because in 1994 there were no M52 E36s if I'm right. Or, perhaps it was a very, very early one. I thought the M52 only came in 1996 or perhaps late 1995.. Late 94 would be a very early M52..

In that case, and you DME number confirms it, MS41.0, which is the M52 DME, you would indeed need the M52 MS41.0 320i DME..
I think the one you linked on ebay should work.. It's the exact same part number.
Not sure if the chip tuner in my signature would have one with the right specs, but you could ask (send him the exact part numbers, and he'll tell you asap).. You'll be very happy with the improvement for the 50 euro difference.

Here's a cheaper one (non-tuned), 55 pounds: https://www.ebay.co.uk/sch/i.html?_f...44897&_sacat=0 . But it looks like it's been in a harsh environment.

Update: Here's a list of M52 320i DME's:
http://www.bmw-etk.info/teile-katalo...94/12141744897

Seems it's the earliest 320i DME ever made, and it doesn't have a flash chip. So you'd need to replace the EPROM chip to chip tune that DME. Probably not too many tuning options around because it was used for such a short period, and also no EWS, which most later models had standard.

Also checked at realoem. As of August 1994 until October 1995 both the M50 and M52 320i models were manufactured. Interesting.. Didn't know the M52 was available that early. You have one of the first M52's that left the factory.

**Denjeesi** · 08-18-2018, 03:00 PM

Originally Posted by ed323i

Oh, wait, you have an M52 engine.. I think the manufacture date is incorrect then, because in 1994 there were no M52 E36s if I'm right. Or, perhaps it was a very, very early one. I thought the M52 only came in 1996 or perhaps late 1995.. Late 94 would be a very early M52..

In that case, and you DME number confirms it, MS41.0, which is the M52 DME, you would indeed need the M52 MS41.0 320i DME..
I think the one you linked on ebay should work.. It's the exact same part number.
Not sure if the chip tuner in my signature would have one with the right specs, but you could ask (send him the exact part numbers, and he'll tell you asap).. You'll be very happy with the improvement for the 50 euro difference.

Here's a cheaper one (non-tuned), 55 pounds: https://www.ebay.co.uk/sch/i.html?_f...44897&_sacat=0 . But it looks like it's been in a harsh environment.

Update: Here's a list of M52 320i DME's:
http://www.bmw-etk.info/teile-katalo...94/12141744897

Seems it's the earliest 320i DME ever made, and it doesn't have a flash chip. So you'd need to replace the EPROM chip to chip tune that DME. Probably not too many tuning options around because it was used for such a short period, and also no EWS, which most later models had standard.

Also checked at realoem. As of August 1994 until October 1995 both the M50 and M52 320i models were manufactured. Interesting.. Didn't know the M52 was available that early. You have one of the first M52's that left the factory.

That is what I wrote in my very first post, M52 engine

Yes I think it was the 15th November 1994 where the car was build, indeed one of the first ones very cool

So can I install any M52 320i MS41.0 DME? Or do I have to have the same parts number?

**ed323i** · 08-18-2018, 06:07 PM

I think I saw 1994 and my mind immediately thought: OK, M50tu (vanos), and I skipped over the m52 part.. Then today I reread the first lines of your post and saw it, and first thought it must be a typo.. But not so ;-) .

I think you're 100% safe with the exact same part number.. With all others, I really can't guarantee anything, because they might have EWS, and if you car has no EWS wiring and devices, then you might get in trouble. They all are MS41.0, so the DME "thinks" and act the same, but with the EWS models there are some extra electronics and wires added, and that will probably not work out.

Update: Here's a nice link on the EWS stuff.. As of January 1995 I think all (or at least most) E36s had EWS-II standard, and had it integrated in the DME. https://www.turnermotorsport.com/e/t-faq-ews
With EWS-I which your car should have, the DME wasn't really integrated with the EWS.

Update 2: Reading more about EWS in the link above, I think there is a good chance a more modern MS41.0 DME with flash-rom WILL work in your car, as long as the EWS code is deleted from the DME. There is probably someone on this forum that has hands-on-experience with this situation.. The way I see it: if a DME with EWS-delete works in an E30 (that has no EWS electronics whatsoever), then it should also work in your non-EWS or non-EWS-II E36. I think it's worth the try to get a chip-tuned (with EWS-delete), more modern DME, and get those 10 extra HP out of your M52B20. If it really doesn't work, you won't have a hard time selling the DME on, as it's really cheap (150 euro for a properly chip-tuned DME)..

**Denjeesi** · 08-20-2018, 03:07 AM

Originally Posted by ed323i

I think I saw 1994 and my mind immediately thought: OK, M50tu (vanos), and I skipped over the m52 part.. Then today I reread the first lines of your post and saw it, and first thought it must be a typo.. But not so ;-) .

I think you're 100% safe with the exact same part number.. With all others, I really can't guarantee anything, because they might have EWS, and if you car has no EWS wiring and devices, then you might get in trouble. They all are MS41.0, so the DME "thinks" and act the same, but with the EWS models there are some extra electronics and wires added, and that will probably not work out.

Update: Here's a nice link on the EWS stuff.. As of January 1995 I think all (or at least most) E36s had EWS-II standard, and had it integrated in the DME. https://www.turnermotorsport.com/e/t-faq-ews
With EWS-I which your car should have, the DME wasn't really integrated with the EWS.

Update 2: Reading more about EWS in the link above, I think there is a good chance a more modern MS41.0 DME with flash-rom WILL work in your car, as long as the EWS code is deleted from the DME. There is probably someone on this forum that has hands-on-experience with this situation.. The way I see it: if a DME with EWS-delete works in an E30 (that has no EWS electronics whatsoever), then it should also work in your non-EWS or non-EWS-II E36. I think it's worth the try to get a chip-tuned (with EWS-delete), more modern DME, and get those 10 extra HP out of your M52B20. If it really doesn't work, you won't have a hard time selling the DME on, as it's really cheap (150 euro for a properly chip-tuned DME)..

No problem, now you know more

I think I will go with a remaped more modern DME with the EWS delete, if it isn't compatible I'm going to sell it or return it if that's possible.

I could even buy a cheep stock M41.0 and replace the chip inside with a remaped one, migh also work.

**ed323i** · 08-20-2018, 08:14 AM

Originally Posted by Denjeesi

No problem, now you know more

I think I will go with a remaped more modern DME with the EWS delete, if it isn't compatible I'm going to sell it or return it if that's possible.

I could even buy a cheep stock M41.0 and replace the chip inside with a remaped one, migh also work.

That's what i would do too, go for the remapped, EWS-delete more modern flash-based DME.
With the stock DME, theoretically you could replace the EPROM chip, but you'd have to find a tune for that specific DME and that might prove very difficult, as the DME was used only a few months.

Please let us know the results! I think the chance of your problems being caused by the DME is very high.

**Denjeesi** · 08-22-2018, 03:15 AM

Originally Posted by ed323i

That's what i would do too, go for the remapped, EWS-delete more modern flash-based DME.
With the stock DME, theoretically you could replace the EPROM chip, but you'd have to find a tune for that specific DME and that might prove very difficult, as the DME was used only a few months.

Please let us know the results! I think the chance of your problems being caused by the DME is very high.

Yes I will tell you how it goes, I will also do a compression test today just to see if there is really nothing wrong with the compression, just to make sure.